Control of Ignition Temperature in Hybrid Thermite-Intermetallic Reactive Systems

Abstract

Thermite compounds have received a renewed interest due to their ability to store large quantities of energy that is comparable to conventional energetic materials. Such reactive materials can be manipulated to create a nanolaminated structure. It has been shown that an increase in the fraction of nanolaminated particles can reduce the ignition temperature and increase reactivity. In the present study, methods to lower the ignition temperature of aluminium copper-oxide (Al-CuO) are assessed. Arrested reactive milling (ARM) was used on stoichiometric Al-CuO powders to increase the nanolamination and reduce the ignition temperature to 840 Kelvins (K). Milling alone not only reduced the ignition temperature slightly, but for milling times greater than 30 minutes, intermediate phases were produced, which had negative impacts on the reaction characteristics. Another method to reduce the ignition temperature of Al-CuO involved creating a hybrid mixture using a compound with a lower ignition temperature to further decrease the ignition temperature of Al-CuO. ARM was used to lower the ignition temperature of a nickel aluminium (Ni-Al) intermetallic compound down to 480 K. Hybrid mixtures were then created with varying concentrations of milled and unmilled Al-CuO-Ni. Powders were then tested in a tubular furnace to determine the ignition temperature dependence on heating rate and concentration of constituents. It has been shown that an unmilled hybrid mixture with 75% and 50% concentration of Al-CuO has an ignition temperature of 840 K. Higher concentrations of Ni-Al resulted in lowered ignition temperatures which varied between 600 K and 480 K. A milled hybrid mixture has lower ignition temperatures than an unmilled mixture. It was shown that a milled hybrid mixture with a 75% concentration of Al-CuO has an ignition temperature of 840 K, corresponding to pure Al-CuO. The ignition temperature of the milled hybrid mixture was reduced to approximately 520-620 K for concentrations of Ni-Al of 50%, and 473-573 K for concentrations of 75% Ni-Al.